Collaborative Research: Testing hypotheses of latest Pleistocene paleo-environmental collapse, Northern Channel Islands, California

测试最新更新世古环境崩溃假说，北海峡群岛，加利福尼亚本研究将描述在最新更新世期间发生在加利福尼亚北海峡群岛（NCI）上的戏剧性古环境变化的性质和时间。特别是，我们将验证一个主要假设，即岛屿的森林砍伐、河流的恶化、山体滑坡和广泛的焚烧是由火情急剧变化引起的同步事件——可能与第一批人类的到来和猛犸象的灭绝有关。其他次要假设也将得到检验，包括由逐渐的气候变化引起的变化、由气候驱动的火灾频率逐渐增加、海平面上升导致的生态系统减少，或约13ka的影响事件。最近对NCI的研究发现，在13000 cal yBP左右的关键事件的年龄越来越趋同，包括：(1)古植物从针叶树植被向非树木植被的转变，(2)低地沉积的开始，(3)更新世滑坡；(5)第一批人类的到来，(6)猛犸象的灭绝。另一个研究小组提出了约12.9 ka的撞击事件。这项工作将通过以下方式来验证这些假设：详细描述最新更新世序列的地层学，OSL和放射性碳定年，孢粉学和古植物学，ois2后海侵的局部制图，木炭沉积的表征，以及通过最新更新世-全新世序列对微球和其他潜在的外星指标进行系统采样。火灾是一种记录在案的机制，通过这种机制，少数人可能会对自然系统产生重大影响。在人类向新大陆迁移的先锋队中，区域人为环境影响可能意味着以前未认识到的时间和规模。

Testing a Hypothesis of Latest Pleistocene Paleo-environmental Collapse, Northern Channel Islands, CaliforniaThis research will describe the nature and timing of dramatic paleo-environmental changes that occurred on the Northern Channel Islands (NCI) of California during the latest Pleistocene. In particular, we will test the primary hypothesis that deforestation of the islands, fluvial aggradations, landsliding, and widespread burning were synchronous events caused by a sharp change in fire regime - per haps associated with the arrival of the first humans and the extinction of mammoths. Other secondary hypotheses will be tested, including changes caused by gradual climate change, gradual climate-driven increases in fire frequency, ecosystem reduction due to sea-level rise, or an impact event at ~13ka. Recent research on the NCI has seen a growing convergence in the ages of key events around 13, 00 cal yBP, including (1) a paleobotanical shift from conifer cover to non-arboreal vegetation, (2) onset of lowland aggradations, (3) Pleistocene landsliding: (4) deposition of charcoal and disseminated carbon; (5) arrival of the first humans, and (6) extinction of mammoths on the NCI. Another research group has suggested an impact event at ~12.9 ka. This work will test these hypotheses through: detailed description of the stratigraphy of latest Pleistocene sequences, OSL and radiocarbon dating, palynology and paleobotany, local mapping of the post-OIS2 transgression, characterization of charcoal deposition, and systematic sampling of microspherules and other potential extraterrestrial indicators through the latest Pleistocene-Holocene sequence. Fire is a documented mechanism by which small numbers of humans may have large impacts on natural systems. Regional anthropogenic environmental impacts at the vanguard of human migration into the New World might imply a timing and magnitude not previously recognized.